- Author: Kathy Keatley Garvey
When the 105th annual UC Davis Picnic Day takes place Saturday, April 13, thousands of visitors will explore the campus. It promises to be informative, educational and entertaining.
But over at Briggs Hall, home of the UC Davis Department of Entomology and Nermatology, “special guests” will include bugs.
There will not only be cockroach races, maggot art, and displays of bees, ants, aquatic insects—and more!—but huge images of vectors, the incredible macro photography of medical entomologist/geneticist Geoffrey Attardo, assistant professor, UC Davis Department of Entomology and Nematology.
Virtual Reality Bugs
Attardo will be demonstrating “Virtual Reality Bugs” where youths and adults can watch 40-foot tall, three-dimensional insects and spiders. And in his medical entomology display, he will be exhibiting metal prints of vectors, including a tsetse fly, kissing bug, deer tick, mosquito, stable fly, cat flea and bed bug.
You wouldn't want to encounter a bed bug in your bed, or a flea or tick on your dog, or a mosquito on your arm. You may not even know what they look like up close. But with these images, you can see what's bugging you or your pets.
And with the Virtual Reality Bugs, participants can select what they want to see--or what's towering over them. The list includes a black widow spider, ant, beetle, grasshopper, damsel fly, cicada, cockroach, and a tsetse fly. Each person will be limited to about 30 seconds to accommodate the crowd.
The Briggs Hall activities run from 9 a.m. to about 4:30, while activities at the Bohart Museum of Entomology, will be offered from 11 a.m. to 2 p.m.
TheBohart Museum will focus on the theme, "Will Travel for Bugs: TheBohart Museum of Entomology's Collections from Around the World." It's nominated for a people's choice award, as is the honey tasting exhibit at Briggs Hall. Participants will sample meadowfoam, sage, cotton and buckwheat. QR codes will be at each site. (See news story about the activities at both sites.)
Vectors
But back to the vectors. Did you know that the Bohart Museum provides information or fact sheets on its website at http://bohart.ucdavis.edu/insect-info-sheets.html?
You can learn about some of the vectors that will dwarf you when you visit Briggs Hall.
For example, ticks!
"Ticks are blood-feeding external parasites of mammals, birds, and reptiles throughout the world," writes Lynn Kimsey, director of the Bohart Museum and UC Davis professor of entomology. "They are not insects rather they are arachnids, the same group that includes spiders and scorpions. There are two different groups of ticks, the hard ticks (Ixodidae) and soft ticks (Argasidae). Both are important vectors of pathogens to humans and animals throughout the world. Some diseases of current interest in the United States caused by tick-borne pathogens include Lyme Disease, Rocky Mountain Spotted Fever, and tick-borne Relapsing Fever (soft ticks)
"Many ticks seek hosts by 'questing.' Questing ticks crawl up the stems of grass or perch on the edges of leaves in a typical posture with the front legs extended. Certain chemicals, such as CO2, as well as heat and movement cause questing behavior. Ticks climb onto a potential host that brushes against their extended front legs. Once on a host hard ticks may feed for several days to several weeks.
And fleas!
"Fleas are bloodsucking parasites of humans, livestock and pets," Kimsey writes. "Only adult fleas feed on blood, which they obtain with their piercing/sucking mouthparts. Adult fleas blood feed on birds and mammals.Adult fleas are laterally flattened, wingless insects. They have a small eye spot on the side of the head, and a row of stout spines along the side of the head and the back of the thorax. Adult fleas travel rapidly by jumping, using their legs and a spring-like mechanism in the body. They are capable of spectacular leaps, covering distances up to one hundred times their body length
"The most common flea found on household pets, such as cats and dogs, is the cat flea, Xenopsylla cheopis."
Read the Bohart fact sheets and then check out Attardo's images.
EGSA T-Shirts
If you'd rather wear your bug on your shirt, the Entomology Graduate Student Association (EGSA) can oblige. They have scores of insect-themed t-shirts, ranging from beetles and honey bees to wanna bees. The newest t-shirts in the line-up include two designed by talented doctoral student/ant specialist Jill Oberski of the Phil Ward lab. One is a take-off of American Gothic, the 1930 painting by Grant Wood, except with entomologists holding a net in front of Briggs Hall, UC Davis campus, instead of the farmers holding a pitchfork in front of their farmhouse. The other Oberski t-shirt celebrates the 45th anniversary of UC Davis Picnic Day cockroach races. Roaches rock! Forensic entomologist Robert Kimsey, co-chair of the department's displays at Picnic Day, rears cockroaches in his lab, but on Picnic Day, they're ready to race! Doctoral candidate Brendon Boudinot, EGSA president and co-chair of the department's displays, says the roaches will race on a new racetrack.
Doctoral student/nematologist Corwin Parker of the lab of Steve Nadler, professor and chair of the UC Davis Department of Entomology and Nematology, also came up with a clever idea for a t-shirt. You know how cicadas can be REALLY loud? He drew one plugged into an amp. Now, that's REALLY loud! You can buy EGSA t-shirts at Briggs Hall on Picnic Day or order them online at https://mkt.com/UCDavisEntGrad/ after Picnic Day.
- Author: Lynn M. Sosnoskie
According to a previous ANR blog post, the 2013 processing tomato crop in California is experiencing worse-than-usual curly top problems, which is caused by a complex of Beet Curly Top Viruses (BCTVs) (Processing tomatoes face critical threat: curly top). Infections are generally lethal to young transplants. Older, more developmentally mature plants will become chlorotic and stunted with cupped leaves and curled petioles. Leaf veins will often turn purple. Fruit set can be significantly impacted (Heflebower et al. 2008).
BCTVs are members of the Geminiviridae family of viruses (specifically, the Curtovirus genera). Viruses in this family have circular, single-stranded DNA genomes that are encapsulated in a 'twinned' (hence the name 'Geminiviridae') set of icosahedral protein shells. According to Chen et al. (2010), three distinct viruses are responsible for curly top disease in the western United States: Beet Curly Top Virus (BCTV, formerly the Cal/Logan strain), Beet Mild Curly Top Virus (BMCTV, formerly the Worland strain) and Beet Severe Curly Top Virus (BCSTV, formerly the CFH strain). BMCTV and BSCTV were the predominant pathogens associated with curly top in processing and fresh market tomatoes in California, as determined by surveys conducted between 2002 and 2008 (Chen et al. 2010).
The viruses that cause curly top have an extremely wide host range (>300 species), including crops (i.e. beets, tomatoes, peppers, cucumbers, watermelon, spinach), weeds (i.e. filaree, perennial pepperweed, Russian thistle and mustard species), and native shrubs (i.e. buck brush [Ceanthus cuneatus]) (Chen et al. 2010; Creamer et al. 1996; Davis et al. 1998). Symptomology can vary dramatically among species; crops tend to exhibit obvious signs of infection, whereas weeds and perennial shrubs are generally asymptomatic (Creamer et al. 1996; Davis et al. 1998). Differences in disease pressure (and viral concentration) are likely due to the varying degrees of virulence among the virus strains, pathogen/host interations that affect viral replication and leafhopper feeding preferences.
Similar to the virus, its vector, the beet leafhopper (Circulifer tenellus), also has a wide host range (Chen et al. 2010; Creamer et al. 1996; Davis et al. 1998; Heflebower et al. 2008). Adult leafhoppers migrate into the coastal range foothills in late fall to overwinter on perennial weeds (i.e. Russian thistle). Their eggs are oviposited on annual species (i.e. buckhorn plantain) that germinate in the following spring. The leafhopper nymphs feed on infected plants, thus acquiring the virus. Mature beet leafhoppers carry the virus to the Central Valley during their spring flights. Successive generations of leafhoppers will feed on both weeds and crops (transmitting the virus while doing so) before the remaining adults migrate back to the foothills for winter. Warm and windy conditions in the springtime increase virus problems, as this facilitates the 'dry-down' of the foothills reservoir species and brings about the start of the migratory cycle (Chen et al. 2010; Creamer et al. 1996; Davis et al. 1998; Heflebower et al. 2008). Additionally, both Chen et al. (2010) and Creamer et al. (1996) suggested that the viruses could survive, year round, in host plants located within the San Joaquin Valley, thereby precluding the need for yearly re-introductions.
Curly top can be confused with tomato spotted wilt, which is caused by the Tomato Spotted Wilt Virus (TSWV, genus Tospovirus, family Bunyviridae). Tomato Spotted Wilt Virus is extremely complex, relative to the BCTVs. The TSWV virion consists of three negative, single-standed, ribonucleoprotein-encapsulated RNAs (the Large [L], Middle [M] and Small [S] stands), which are enclosed, along with an RNA-dependent polymerase, in a host-derived membrane bilayer (Sherwood et al. 2003). TSWV can infect more than 1000 species across 85 families, including: tomato, pepper, potato, eggplant, radicchio, begonia, geranium, sowthistle, cheeseweed, purslane and prickly lettuce. Symptoms of TSWV vary with respect to host plant identity, plant age and environmental conditions, although the most common symptoms on tomatoes include: chlorosis, wilting, bronzing and the development of necrotic spots. Concentric rings may develop on infected fruit. The tospoviruses are vectored exclusively by thrips (Thysanoptera: Thripidae). Frankliniella occidentatlis, the western flower thrips, is considered to be the most important TSWV vector species because of its global distribution (Sherwood et al. 2003).
The management of viral diseases can be quite difficult. With respect to curly top, control strategies could include: altering the timing of tomato plantings to avoid exposing young transplants to the early migration of leafhoppers, increasing planting densities to compensate for losses and discourage visitation by leafhoppers, and eliminating weeds and tomato volunteers following harvest. The California Department of Food and Agriculture manages a statewide program (Curly Top Virus Program) designed to control the beet leafhopper. For tomato spotted wilt, growers are advised to ensure that their transplants are both virus and thrips free. Fields should be monitored for both thrips and viral symptoms. Thrips management should occur early in crop development; if reasonable, symptomatic plants should be removed. As with curly top, weeds and volunteers should be controlled. The use of resistant varieties is encouraged (the resistances of some tomato varieties to TSWV are noted here).
References:
Chen et al. 2010. Characterization of curtoviruses associated with curly top disease of tomato in California and monitoring these viruses in beet leafhoppers. Plant Disease 94:99-108
Creamer et al. 1996. Epidemiology and incidence of Beet Curly Top Geminivirus in naturally infected weed hosts. Plant Disease 80:533-535.
Davis, et al. 1998. Curly top virus found in perennial shrubs in foothills. California Agriculture. 52:38-40.
Heflebower et al. 2008. Curly top of tomato. Utah Pests Fact Sheet PLP-007. http://extension.usu.edu/files/publications/factsheet/curly-top-tomato08.pdf
Sherwood et al. 2003. Tomato spotted wilt. The Plant Health Instructor. http://www.apsnet.org/edcenter/intropp/lessons/viruses/Pages/TomatoSpottedWilt.aspx
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